Optical Transport Network (OTN) is a transport network in the optical layer network based on Wavelength Division Multiplexing (WDM) technology. The OTN is a backbone network of the next generation, and it is a digital transport system and optical transport system of new generation regulated by recommendations of a series of InterNational Telegraph Union Telecommunication Standardization Sector (ITU-T), such as G.872, G.709 and G.798. OTN solves problems such as weak service scheduling capability, weak networking capability and weak protection capability regarding the transparent wavelength or sub-wavelength services of the traditional WDM network. OTN mainly defines an OTUk frame structure. By defining the OTUk frame structure, the user signal adaptation problem and the transparent wavelength or sub-wavelength services scheduling problem of the WDM network can be solved. Also, as the OTUk frame structure has plenty overhead, reliable transmission of the optical layer can be guaranteed, and the problems such as weak protection capability of the traditional WDM network are solved. Through the OTN technology, service scheduling can be achieved more flexibly, the reliability of transmission can be improved, the protection capability of network can be enhanced, and the network can be monitored.
Defined according to recommendations of ITU-T, Synchronous Digital Hierarchy (SDH) is a technical system formed by multiplexing method, mapping method and related synchronization method. The SDH is an information structure in which the corresponding level is provided for the transmission of digital signals at different speed. It can achieve various functions such as effective network management, real-time service monitoring, dynamic network maintenance and intercommunication between equipments from different manufacturers. It greatly improves the utilization of network resources, reduces the management and maintenance expenses, and achieves flexible, reliable and highly efficient network operation and maintenance. Therefore, nowadays the SDH becomes a development and application hotspot of the transmission technology of the information field in the world, and attracts extensive attention. In the related optical communication technologies, network protection switching is executed based on SDH, but there is no method supporting protection switching in OTN.